Laser smashes light-speed record
Special relativity prevents any object with mass travelling at the speed of light, and the principle of causality – the notion that the cause comes before the effect – is used to rule out ...
Microscopy: two lasers are better than one
Stefan Hell and co-workers at Gottingen have adapted a technique known as fluorescence microscopy. In this form of microscopy the specimen is irradiated at a wavelength which excites either natural or...
Laser control of X-ray output
In harmonic generation a short pulse of intense radiation is focussed into a gas of atoms. The laser-atom interactions are highly nonlinear, and a number of the input photons effectively combine to ge...
Looking inside quantum dots
Manfred Bayer of the University of Wurzburg in Germany, and co-workers in Wurzburg and the National Research Council of Canada in Ottawa, studied indium gallium arsenide quantum dots grown on a galliu...
Polymer lasers without mirrors
The waveguide structure was created by pouring a mixture of copolymer solution and molecular laser dye into a mould situated on top of a silicon wafer. The solution was allowed to solidify over 12 hou...
Read article: Nuclear physics with lasers
Nuclear physics with lasers
About 20 years ago Toshi Tajima and John Dawson, then at the University of California at Los Angeles, suggested that laser-produced plasmas could be used to accelerate particles to high energies. The ...
Electrons trapped by laser beam
The experiment was carried out inside a vacuum chamber filled with a low density nitrogen or argon gas. A wave plate – in the form of a small circular piece of material – was inserted into...
Water transfers energy at ultrafast rate
As a water molecule is excited by the laser pulse, it can only drop back to a less excited state by releasing the excess energy. This energy causes the O-H bonds to stretch and vibrate. As the bonds v...
Ultrafast X-rays watch matter melt
The germanium sample was bombarded with powerful laser pulses to excite the electrons and cause thermal melting. In this process, unlike normal melting, the metallic crystal goes from a cold solid to ...
Reflections on the life of a laser pioneer
Charles Townes has written a biography – but it is not clear if it is his own or that of the laser. The laser is now such a feature of our everyday life that the remarkable story of its birth ne...
